Electronic pulse generator



y 1950 B. WELLMAN 2,506,529

ELECTRONIC PULSE GENERATOR Filed Sept. 12, 1946 STEEP R/Sf x 2% APE/F/OD/C 0&4) E E s T/Mf [72 van to?" Bertram WeZlman Q3 TM, W am Patented May 2, 1950 ELECTRONIC PULSE GENERATOR Bertram Wellman, Lincoln, Mass, assignor to The Elcctrodyne Company, Boston, Mass, a corporation of Massachusetts Application September 12, 1946, Serial No. 696,590

11 Claims.

The present invention relates to apparatus for generating and controlling electric impulses of non-sinusoidal configuration, particularly with steep fronts.

In various fields of applied electricity it is desirable to Work with electric impulses of the above mentioned configuration, of adjustable duration and frequency, and applicable singly, in groups, or automatically repeated at an adjustable frequency. Such impulses are for exan: ple used as stimuli in certain physiological tests, Where they are applied with stylus probes to nerve or muscle tissue. The usefulness of such tests depends a great deal upon the easy adjustability, within Wide ranges, of impulse strength and fre quency, and also on the possibilit of applying single impulses with the same equipment from which impulse series or groups are derived.

It is one of the principal objects of the present invention to provide a simple, comparatively inexpensive, and yet rugged, dependable and adaptable apparatus for generating electric impulse series or single impulses which reach their maximum value very rapidly and decay immediately upon having reached that value.

Other objects are to provide electronic ratus which generates with a minimum of circuit elements non-sinusoidal electric impulse series of controllable duration and frequency, of selectively predetermined polarity, of selectively adjustable energy contents, and if desired accompanied by synchronized but independently generated signal impulses; to provide apparatus of the above mentioned type which permits, selectively with the aid of a simple change-over control, the generation either of single impulses or impulse groups or or" an infinite series of impulses of similar characteristics but predetermined frequency; and to provide a circuit which, upon operation of a control switch, delivers a single steep front impulse which can only be repeated after resetting of the switch.

In one of its aspects, the apparatus according to the invention employs an electron discharge device having anode and cathode connected to a source of direct current and a control electrode which is maintained at a substantially constant potential, impedance means and a switch in the (Cl. I'll-97) generation.

for physiological test purposes.

signal impulses which are in exact synchronisin with the principal impulses, by way of discharging an auxiliary or signal capacitor through a discharge tube which is triggered by a control electrode connected to the network carrying the main or principal impulses.

In a further aspect, the circuit according to the invention supplies a single electric energy impulse or a predetermined number of such impulses, by means of an electric discharge device having anode and cathode connected to a direct current source and a control electrode, a. capacitor in the connection from the cathode to the positive side of the source, another capacitorln the connection between the cathode and the negative side of the source, these capacitor means being so dimensioned that the simultaneous charging thereof across the source causes discharge of the first mentioned capacitor through the discharge device Whose control potential depends upon the potential of the cathode and hence upon the relation of the potential drops across the two capacitors. The second capacitor continues to be charged during the discharge or discharges of the first condenser, until it brings the cathode potential close enough to the electrode potential to render discharge of the first capacitor impossible, thus terminating impulse If the second capacitor is small enough for the purpose, discharge of the first capacitor is only looked after a group of impulses (their number depending upon the relative values of the circuit elements) has been generated.

Additional features of the circuit according to the invention are selection of polarity of the impulses by means of a switch in the secondary circuit of a transformer link in the output circuit, and selective supply of either an unlimited series of impulses or one or a predetermined number of impulses whereby all circuit elements which are employed for furnishing the unlimited impulse series are also utilized for operation with one or a preselected number of impulses, the change from one operation to the other being provided by switch'means rendering the above mentioned second capacitor ineffective for the purpose of generating an unlimited sequence of impulses.

These and other objects, aspects and features will appear from the following description ofa typical, practical embodiment illustrating the novel characteristics of my invention. This description r iers to a drawing in- Which- Fig. 1 is the circuitv diagram of a. stimulator I constructed. according to the present invention;

' sistor R3.

through limiting resistor RI I.

Fig. 2 is a diagram illustrating the configuraticn of the impulses furnished apparatus according to Fig. l; and

Fig. 3 is a component of the circuit diagram of Fig. 1, illustrating the operation of circuit when for delivery or a single impulse or oi a limited series of impulses.

In the stimulator according to Fig. l, a transformer T, supplied from terminals a, c of a standand alternating current supply line, feeds into a tube GI is connected to a tap pi intermediate to voltage apportioning resistors RI, R2 which are connected across the direct current supply d, c, thus being supplied with constant voltage and. retaining grid G! at substantially constant potential. The cathode kl is connected to a point p2 of a discharge and timing network Nt.

The discharge network Ni incorporates a main capacitor Cl which isconnected between terminal p2 and supply line (i and bridged by a safety re- Between terminal 102 and the other direct current supply terminal are connected,

through a starting switch S, a resistor R4, and a resistor R which is adjustable, having for example a movable tap v. A point p3 between resistors R4 and R5 is connected to the ofi terminal of switch 8 through a control capacitor C2, this 0 terminal being also connected to a contact t which can be joined to the negative supply wire 0 by way of movable tap e which, when contacting it, leaves adjustable resistor R5.

An intermediate tap p4 of transformer primary To is connected to the positive supply wire d, whereas transformer secondary Ts is connected through a pole changing, double pole double throw switch st, to the output or probe'network An indicator lamp Gl, for example of the gaseous discharge type, may be connected to output'wireo.

In order to permit selection of suitable output voltages, network Np incorporates voltage dividing resistors El, E8 of different values, and selooted by means of a switch 82. For fine adjustmentof the voltage an adjustable resistor R?! with tap it is provided in series with R! or R8. For the purpose of impedance matching a resistor R! 0 may he provided which is connected in parallel to R8 and R9 when switch .92 incorporates R8 in the output network. The main output terminals 11, I2 are connected to tap in and supply wire .0,

V respectively.

Forthe purpose of roviding auxiliary impulses, the followin'g signal network Ns is provided. An

electric discharge tube G2,fforexample of the gas filled thermionic type, is with its anode c2 connected to the direct current supply wire d,

The anode connection contains further the primary of a signal transformer-T2 whose secondary feeds into signal output terminals l5, -6. A signal capacitor C3 is connected between "a oint 795 between/transfformer T2 and resistor RI I, and upply wire 0. The control electrode 172 of-tube G2 is connected to the end terminal of transformer Tl, through resistor RI5 and capacitor C5. A point 216 intermediate capacitor C5 and resistor R15 is connected to supply wire 0 through a control resistor BIS. The cathode k2 of tube G2 is connected to negative supply wire 0 through capacitor C8 which is bridged by resistor Rlfi.

The arrangement according to Fig. I. operates as follows, assuming first that it is desired to deliver a continuous series of impulses.

With alternating current supply line we energized, the cathodes of tubes G are heated and ready for operation, and the direct current supply system .01, c, is supplied through networks N1" and N1. Tap ois disconnected from the single operation contact 15 and connected to a selected section of R5, so that control capacitor C2 is effectively disconnected from the circuit.

When switch S is moved from the ofi to the on position, capacitor Cl charges at a rate determined by the setting of tap v on adjustable resistor R5, and the value of fixed resistor R4. With capacitor Cl charging, the potential of cathode kl becomes more negative relatively to the constant potential of control electrode gl, and when the proper voltage between kl and pi is reached, tube G! will fire. Capacitor CI thereupon rapidly discharges through the circuit Cl-Gl--Tp-dCl, its maximum voltage being almost immediately applied to primary Tp. The discharge impulse is transmitted through secondary Ts and switch s! to the probenetwork Np, where it appears at output terminals ll, 12 with the polarity and voltage selected by means of switches sl, s2 and tap w. The discharge continues with a periodic decay, until the impulse ceases altogether when the potential of point 102 and of cathode kl has become more positive, appreaching that of grid gl sufficiently to render the tube non-conductive.

With switch S left in on position, condenser CI again charges, and cathode kl becomes more negative until the next impulse begins with Cl again discharging through GI.

By reversing switch sl, the polarity of the impulses can be changed. The gaseous discharge lamp Gl indicates to the operator the occurrence and polarity of each'individual impulse. The re sistor R3 prevents through comparatively gradual discharge a possible accidental sudden discharge of capacitor R5 if leaks should be present in the circuit.

The impulses available at terminals H, l2 have the approximate configuration indicated in Fig. 2, with steep wave fronts and aperiodic decay flanks. The spacing of the impulses, or in other words the frequency of the impulse series can be cludingtube (3-2, transiormerTZ, and terminals 15, it. It is, however, often desirable to have available impulses which are exactly synchroinized with, but are otherwise, such as regarding their energy, independent ofithe output impulses proper. Such auxiliary impulses are ,for example used for energizing a .relay magnet which in turn operates an impulse indicating signalling device or apparatus for marking a recording strip with timing indicia.

The signal network Ns operates as follows.

The impulse due to the discharge of capacitor Cl through transformer Tl causes current to flow through control resistor RIB which raises the potential of point 178 and of grid 92 sufficiently to cause firing of tubs G2. Capacitor C3, which is normally charged due to its connection between wires d and c of the direct current supply, thereupon discharges through tube G2 and transformer T2, delivering an auxiliary impulse at terminals l5, It.

If it is desired to deliver a single impulse or a predetermined number of impulses, for instance, a group of two or three impulses, switch S is moved to the "ofi position, and tap v is brought into contact with single terminal 15, connectin control capacitor 02 between cathode kl and supply terminal 0. This mode of operation will be explained with particular reference to Fig. 3 which shows capacitor C2 in effective connection, with contacts 12 and t in electric contact.

When switch S is moved from the off to the on position, both capacitors Cl and C2 begin to charge.

If the capacitance value of capacitor C2 is so selected that it will not be fully charged before the firing voltage between cathode kl and grid gl is reached, the potential of p2 will remain sufficiently low to cause firing of tube GI, and repeated firing thereof, until capacitor C2 is charged sufiiciently to raise the potential of 112 and of cathode lcl to a value approaching that of the potential of gl so that tube GI becomes nonconductive.

If capacitor C2 is large as compared to Cl, the latter will discharge several times before C2 is sufliciently charged to render the tube nonconductive. On the other hand, if the value of C2 is so selected that the voltage between kl and gl is below the firing value just after Cl has once discharged, a single impulse will be delivered before C2 is sufiiciently charged to bring cathode and grid potentials close enough to render tube Gl non-conductive. By properly selecting, or adjusting the value of capacitor C2, discharge of single impulses, or of groups of a preselected number of impulses can be provided. In order to repeat this mode of operation, the switch S has to be brought into off position, and then back into on position to re-initiate the single impulse or impulse group discharge as above described.

A practical apparatus according to Fig. 1 comprises the following circuit elements:

Capacitors Cl mfd 0.5 oz mfd o. 1 C3 imfd 25 It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. Apparatus for generating controlled elec tric impulses, comprising a source of direct current having a positive output terminal and a. negative output terminal; an electric discharge device having an anode, a cathode and a control electrode; circuit making means including a resistor connecting the cathode with the negative output terminal; a transformer having a secondary, and a primary with a terminal connected to said anode and an intermediate tap connected to said positive output terminal of said source; main output terminals connected to said secondary; means for maintaining the electrode at substantially constant positive potential of lesser magnitude than that of the positive terminal; a discharge network including a capacitor; and an auxiliary signal circuit including an electric discharge tube having a cathode connected to the negative terminal, a control electrode connected to the other terminal of said primary and an anode, an output circuit connecting the tube anode to the positive terminal, and auxiliary output terminals coupled to said output circuit.

2. Apparatus for generating controlled electric impulses, comprising a source of direct current having a positive output terminal and a negative output terminal; an electric discharge device having an anode, a cathode and a control electrode; circu t making means including a resistor and a starting switch connecting the cathode with the negative output terminal; a transformer having a secondary and a primary with a terminal connected to said anode and an intermediate tap connected to said positive output terminal of said source, main output terminals connected to said secondary: voltage apportioning means for maintaining the eelctrode at substantially constant positive potential of lesser magnitude than that of the positive terminal; a discharge network including a capacitor between said cathode and said positive terminal; and an auxiliary signal circuit including an electric discharge tube having a cathode connected to the negative terminal,

' a control electrode connected to the other terminal of said primary and an anode, an output cirouit connecting the tube anode to the positive terminal, and auxil ary output terminals coupled to said output circuit.

3. Apparatus for generating controlled electric impulses, comprising a source of direct current having a positive output terminal and a negative ouptut terminal; an electrc discharge device having an anode, a cathode and a control electrode; circuit making means including a resistor and a starting switch connecting the cathode with the negative output terminal; a transformer having a secondary, and a primary with a terminal connected. to said anode and an intermediate tap connected. to said positive output terminal of said source; main output terminals connected to said secondary; means for maintaining the electrode at substantially constant positive potential, of lesser magnitude than that of the positive terminal; a discharge network including a capacitor;

and an auxiliary signalpcircuit including an electric discharge tube having a cathode connected toitheinegativeterminal,- a-control' electrodeconnected'to the other terminal of -said-primary and an anode, anoutpu-tcircuit including capacitor means; and l transformer means connecting the tube. anode tothe positiveterminal, andauxiliary output-,:terminals coupled to said transformer means".

4. Apparatus for generating ,contro11edelectric impulses, comprising a source of directmcurrent havinaza positive cutputterminai anda negative outputgtermi-nak an electric dischargedevicehavn anode arcathode and,acontrolelectrode; making means including: a. resistor and starti a switch connecting; the, cathode. with the negativepcntput terminal, aiconnection .oetween saidanodeand saidpcsitive terminal 1oa,d means in-esai'ri anode: connection; means: for maintain: ing the. electrodeatsubstantially constant positive potentialioivlesser magnitude than that of the positive terminal; a-connection including capacitorimeans from said cathode ,to, said positiverter minal; and capacitor means insaid circuitv making means betweenlsaid cathode. and said negative :terminal said capacitor means 4. being, so dimensionedone relatively tothe, t enthat the Simultaneous. charging thereof initiates a predetermined number. of discharges ofg-said, first mentioned capacitor meansthroughgsaid load meansrsaidsecond capacitor charging .duringsaid discharges ,ytorthet locking potential between said cathodeend said electrode, when said discharges are terminated,

Apparatus@for generating controlled velectric impulses,,,comprising a source of directcurrent having a positive output terminallanda negative outputlterminal; an electric dischargedevice having an .anode,,a cathodev andia control electrode; circuit making means includinga resistor and-a startingsWitclrconnectingithe cathode with the negative output .terminal;.., a, connection between saidanode and said, positive terminal; transformermeansrinsaid' anode connection; voltage apportioning means for maintaining the electrode at substantially constant positive ,potentialof vlesser magnitude than that ofthe positive terminal; a connection including capacitor'means ,from said cathode to sa d positive terminalrand capacitor means-connectedin series with said-resistor and saidswitchhetween saidocathode and said nega- {and "capacitor charging during said discharges to the- :1'ock n potential. between said cathode and said electrode, when said discharges-aretermihated:

-'6.'::Apparatus for generating electric impulses, comprising a sourceof direct current having a positive outputterminal' and a negative output terminalran electric discharge"devicehaving an anode; a -catho dc and a; control" electrode; circuit making meansincluding a resistor' and=a starting switoh -connectingg-the cathode with the negative outputt'aminal; a connection between" sa-i d anode and saidpo'sitive t'erminal;-load means in said anode connection;- means for maintaining the electrode-atsubstantially constant positive potetitia-Pof lesser magnitude thanth'at-of the posi 'ti-ve terminal; :arconnecticn including capacitor;

means from :said cathode to said- ;p ositiveterminal; ,and 'capacitormeans in said circuit making means between said cathode andsaiinegative terminal said capacitor meanslheing sojdimensioned onerelatively to the otherthatlthetsimultaneous charging thereof initiates i a .7 single; discharge of said, first mentioned capacitor ,means throughysaid load means, said. second capacitor means having upon said single, discharge reached a; charge-large enough to maintain said cathode atiockingpotential relatively to said electrode.

7'. Apparatus for generating electric impulses, com-prising a source of-direct current :havingta positive output terminal and a negative output terminal; 'an :electric discharge device havingaan anodey-a cathode and a control electrode; circuit making :mea'nsincluding a resistor and a'starting switch "connecting the cathode withthe negative, output terminal; a-connection between said anode andrsaid positive 1 terminal; transformer means in said anode connection; voltage apportioning means-for maintaining the electrode 1 atrsubsta-ntially constant positive potential'of lesserunagnitude' than that of' the positive terminal; a con-g nection including capacitor means from said cathode to said positive terminal; and capacitor means in said circuit making means'between said cathode and said negative terminal; said capaci-i tor meansbeing so dimensioned one relativelyito the other'that the simultaneouscharging thereof initiated by said starting switch and controlled bysaid resistor causes a single discharge of said first mentioned capacitor means through said transformer means, said second capacitor means having upon said single discharge reached a charge large enough to maintain said cathode-at locking potential relatively to said electrode;

8. Apparatus for providing an electric impulse; comprising a source of direct currenthaving a positive output; terminal and a negative output terminal; an electric discharge device having an anode, a cathode and a controlelectrode; circuit making means including a resistor and'a start.-

ing switch connecting the cathode with the negative output terminal; a connection between said anode'and said positive terminal; loa'dmeans in said anode connection; means for maintaining the electrode at substantiallyconstant'positive potential of lesser magnitude than that of the positive. terminal; .a connection including capacie tor means from said cathode to said positivegterminal; and capacitor means in'saidcircuit making meansbetween said cathode and-said negae tivaterminal; saidcapacitor means being so dimensionedronerelatively to the other that the simultaneous charging thereof causesdischarge oat-said first mentioned capacitor means-through said load meansgsaidisecond capacitor meansattaining upon a predetermined number of discharges a charge large-enough to render said discharge device non-conductive by maintaining said cathodeat locking potential relatively to said electrodepand' circuit modifying means for ren-v dering said second capacitor means ineffective for the purpose of ;.maintaining said discharge device conductive.

'9; Apparatus-forproviding an electric impulse; comprising a ;source "of direct current havinggak positive output-terminal and anegativeoutput terminal; an electric discharge device having an anode; a cathode and a control electrode; circuit making means including a resistor and astarting switch connecting thecathode' with the'negative output terminal; a connection between said'anode andgsaid positive'terminal; load means in said;

. our 4.

anode connection; means for maintaining the electrode at substantially constant positive potential of lesser magnitude than that of the positive terminal; a connection including capacitor means from said cathode to said positive terminal; and capacitor means in said circuit making means between said cathode and said negative terminal; said capacitor means being so dimensioned one relatively to the other that the simultaneous charging thereof upon closing said switch causes discharge of said first mentioned capacitor means through said load means, said second capacitor means attaining upon a predetermined number of discharges a charge large enough to render said discharge device non-conductive by maintaining said cathode at locking potential relatively to said electrode; and means for shunting said second capacitor'means to render it inefi'ective for the purpose of maintaining said discharge device conductive.

10. Apparatus for providing an electric impulse, comprising a source of a direct current having a positive output terminal and a negative output terminal; an electric discharge device having an anode, a cathode and a control electrode; circuit making means including a resistor and a starting switch connecting the cathode with the negative output terminal; a connection between said anode and said positive terminal; load means in said anode connection; main output means connected to said load means; means for maintaining the electrode at substantially constant positive potential of lesser magnitude than that of the positive terminal; a connection including capacitor means from said cathode to said positive terminal; capacitor means in said circuit making means between said cathode and said negative terminal, said capacitor means being so dimensioned one relatively to the other that the simultaneous charging thereof upon closing said switch causes discharge of said first mentioned capacitor means through said load means, said second capacitor means attaining upon a predetermined number of discharges a charge large enough to render said discharge device nonconductive by maintaining said cathode at locking potential relatively to said electrode; circuit modifying means for rendering said second capacitor means ineffective for the purpose of maintaining said discharge device conductive; and an auxiliary signal circuit including an electric discharge tube having a cathode connected to the negative terminal, a control grid connected to said load means and an anode, an output circuit connecting the tube anode to the positive terminal; and auxiliary output means coupled to said output circuit.

11. Apparatus for providing an electric im pulse, comprising a source of direct current havtive terminal; capacitor means connected in series between said cathode and said negative terminal, said capacitor means being so dimensioned one relatively to the other that the simultaneous charging thereof upon closing said switch and controlled by said resistor causes discharge of said first mentioned capacitor means through said load means, said second capacitor means attain ing upon a predetermined number of discharges a charge large enough to render said discharge device non-conductive maintaining said cathode at locking potential relatively to said electrode; means for shunting said second capacitor means to render it ineffective for the purpose of maintaining said discharge conductive; and an auxiliary signal circuit including an electric discharge tube having a cathode connected to the negative terminal, a control grid connected to said transformer means and an anode, an output circuit connecting the tube anode to the positive terminal; means for applying to said control grid a potential derived from said transformer means; and auxiliary output terminals coupled to said output circuit.

BER'I'RAM WELLMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,093,052 Lord Nov. 2, 1937 2,233,810 Dawson Mar, 4, 1941 2,312,810 Finch Mar. 2, 1943 2,415,943 Fagen Feb. 18, 1947 FOREIGN PATENTS Number Country Date 426.201 Great Britain Mar. 19, 1935 459,572 Great Britain Jan. 11, 1937 OTHER REFERENCES Livingston et al., Electronics, April 1933, pages 96-98. 

